How to check the LP and OPS
#1
10-19-2010, 10:38 AM
#2
10-19-2010, 11:24 AM
Reference Material: Lift Pump/OPS
Here’s another one for the newbie’s out there.
After frequenting the boards for awhile, you’ll notice there seems to be a few things that come around, and around, and around again. One of those things is the Lift Pump, official title: Fuel Lift Pump. So, what is a lift pump, and why does it lift fuel? The lift pump is an in-line fuel pump mounted on the frame rail under the driver’s seat. This is a small electric pump that “helps” bring fuel out of the tank and up to the injection pump. This is to help prevent the expensive injection pump from having to “suck” it’s own fuel all the way up from the tank, which it can do, but can cause damage to itself and it's driver module - more on that in another section*.
Now, that’s pretty straight forward isn’t it? So, why so much fuss about a lift pump anyway? Only because it causes so many issues* when it’s not working.
Will my truck run without the lift pump? Yes it will. How well? Well, to some it will be very noticeable when it’s not working. Some may not even notice.
If I don’t notice that my lift pump isn’t working, I’m okay right? Not exactly. That means that your expensive injection pump is doing all the work in the fuel system. This is NOT a desirable thing. Plus you are setting yourself up for problems*.
How can I tell if my lift pump is working? Do the famous “lift pump test.” How do you accomplish this highly scientific experiment you ask? Very simple. Pop the hood - you’re half way there. Find on the front top of the engine the thermostat housing. You should see a little T-handle valve standing proud there in front of you. (If you have a van, you’ll have a schrader valve down deep behind the oil fill) That T-valve is calling your name saying “turn me.” Pay attention, ‘cause there’s a hose on the end of the T-valve. That hose should have diesel fuel come out of it when the engine is idling and you open the T-valve. When you open the T-valve and the engine is idling, and no fuel comes out, you’ll hear your engine cough, sputter, and die within 30 seconds. If it doesn’t cough, sputter and die with the T-valve open and no fuel coming out, something is plugged up in your fuel system between the fuel filter cannister and the t-valve, perhaps even inside the fuel filter cannister.
If the engine does die, it has emptied the fuel cannister and run out of fuel, so you will need to close the T-valve, then troubleshoot and repair the lift pump system, as follows in the text below.
Now, if you get a continuous stream of fuel out the hose, then close the T-valve and open the plastic air-bleed valve on the top of the metal filter cap - if fuel spurts out there, then congratulations! You are the proud owner of a working lift pump. Not everyone is as blessed as you are at this moment. If you're not, keep reading.
To those not as blessed, pickup reading here. You must determine why you have no fuel supply coming to your injection pump. There are two main culprits to the demise of a lift pump. Either it’s out to lunch, or it’s in the morgue. See, one means it still might work, the other means it’s dead. How do you tell? Check to see if it has power.
First, find the lift pump under the truck. With the engine idling along, pull the plug for the lift pump. You can either use a test light, or a meter to see if you have voltage at the pins. Make sure you get a good connection, otherwise you may condemn the wrong thing. Sometimes it is difficult to get a probe to meet up with the pins inside the plug, so make double sure you’ve got it.
If you have voltage, *chances* are you have a dead lift pump. Not always, but could be a dead lift pump. You may have voltage present under a "no load" condition. This means that voltage may be present when the lift pump is not attached to the circuit, but once the lift pump is connected, the load exceeds the amount of power the circuit can provide because the OPS contacts are creating a high resistance.
Now, if you don’t have voltage, you’ll have to verify upstream from there why there is no voltage present. What is upstream? The infamous OPS (Oil Pressure Switch), or fuse.
What does the OPS have to do with the lift pump? Doesn’t sound right does it to have oil pressure tied to fuel does it? Well, some think that it is a fail safe that in case your engine ever lost oil pressure, it would shut off the lift pump so that engine would stall. Guess what? If you read a little bit ahead of this paragraph, you’ll find 'dat ain’t so'. The real reason why this circuit even exists is because of an accident. In case you should be in a wreck, the last thing you would need is to have your lift pump going to town pumping out that precious, expensive, fuel all over the accident scene. After all, should you be bleeding and having a thumpin’ head - the last thing you’ll be thinking is “Hey, I just paid $2.50 a gallon for that, somebody get a shop-vac!”
Why would the OPS not allow my lift pump to work? Well, from time to time, or shall we say in the corporate world, from dime to dime, some decisions get made. Some for the good, and some for the good of the keepers of the money. The OPS has a set of contacts inside to power the lift pump. This set of contacts are not heavy enough to carry the pathetic amount of current to the lift pump. Sad, I know, but true. So, what ends up happening is your lift pump works fine, but the OPS gets smoked, and then it quits. You think the pump is bad, but it’s not.
Can I just eliminate the OPS? Well, be careful, it is a safety device in some people’s eyes, and to the rest of us, a pain in the rump. Eyes, rump, pick your part. Anyway. If you just “jump past” the OPS, then your pump will run all the time. Not just all the time, but ALL THE TIME. Christmas and Easter included. It will stop when your batteries are dead. Because, while you are grocery shopping, that pump is running. While you are down for a long winter’s nap, it’s pumping. Doesn’t matter if the key is on or off, it’s pumping.
You can make up another circuit and repower it some other way, but be careful how you do it. Some methods have kept the truck running after the ignition is shut off and keys in pocket.
Back to our little friend the lift pump.
The lift pump may fail in a variety of different ways. It may fail “open” meaning that the coil driving the pump no longer has continuity. It may fail mechanically where it is just frozen and nothing moves. It may even (not as often) fail to pump. This means, it makes noise, but doesn’t actually pump.
Does the lift pump make noise? Yes it does. The model year of your truck will determine if your lift pump is powered during the Wait To Start period. That’s the time where that light is on before actually starting your engine. '96-up OBD2 models pre-run the lift pump during WTS and during START, '94-'95 OBD1 models pre-run the lift pump only during START.
The lift pump is characterized by a kind of “purring” noise heard beneath the truck. That noise is quickly drowned out by the engine, once started. When you shut your engine off, you will hear that pump run briefly, maybe only a quick second or two. If you shut your engine off when cold, you will hear the pump run much longer, sometimes up to 30 seconds or more.
A loud clacking noise would indicate no fuel from the tank, or the lift pump is failing or failed - it will run without pumping fuel when the one-way valve(s) fail.
A faint purring or vibration when touching the lp body indicates it is running, but the internal valve-shuttle armature is stuck due to mechanical failure.
So what kind of problems will it cause if the lift pump isn’t working? Many. It will cause all sorts of fuel related issues*. It can be some of the following:
°Stumbling
°Hard Starting
°Lack of Power
°DTC (Diagnostic Trouble Codes) on the Computer
°Stalling
There are be other* issues too, but these seem to be a very (un)popular list.
Where do I get one of these? Some of our site vendors, or any of the popular auto parts stores, or the dealership. More often than not, the auto parts store is a good bet for Ineeditrightnow.
Diesel Place tip: Ask for the version for the '93 6.5TD truck - it is a direct-fit HD replacement that will supply increased fuel pressure and volume to the Inj Pump, which is a good improvement for the '94-up EFI trucks.
FYI: don't mention that you have a '94-up truck, or you will just confuse the parts guy\gal - just describe your truck and drivetrain as a '93.
The ACDelco or Delphi lift pumps are the best replacement, which you can get from O'Reilley's or NAPA , and some of the site vendors, such as Heath Diesel.
Also FYI: the parts-guy\gal may call it a fuel pump.
Are they difficult to change? No - loosen the tubing-fitting nuts on either end, remove and reinstall. Now, if it were only really that easy. Let’s get real here, no camera out-takes…. You’ll end up getting a Diesel bath. You see, depending upon how much fuel is in your tank, there will be fuel that wants to come out of the fuel line. Be ready, because your chances of a date after changing that lift pump dwindle a bunch, unless they are really into the smell of a Diesel cologne. J
After the successful fuel lift system repair you will need to refill the fuel filter cannister - after opening the air-bleed valve, which is the plastic nut on the very top of the metal cap, power up the lift pump, then close the air bleed when the bubbles stop and fuel begins spurting out - if you still get no fuel, you likely have a stopped-up fuel filter - no need to tell you what to do in that event, right?
FYI: after successful fuel flow out the air-bleed, the engine may take a while to restart and run as the Inj Pump begins to draw fuel from the filter, fills internally, then starts pump-up to 1900psi injection pressures.
Here’s another one for the newbie’s out there.
After frequenting the boards for awhile, you’ll notice there seems to be a few things that come around, and around, and around again. One of those things is the Lift Pump, official title: Fuel Lift Pump. So, what is a lift pump, and why does it lift fuel? The lift pump is an in-line fuel pump mounted on the frame rail under the driver’s seat. This is a small electric pump that “helps” bring fuel out of the tank and up to the injection pump. This is to help prevent the expensive injection pump from having to “suck” it’s own fuel all the way up from the tank, which it can do, but can cause damage to itself and it's driver module - more on that in another section*.
Now, that’s pretty straight forward isn’t it? So, why so much fuss about a lift pump anyway? Only because it causes so many issues* when it’s not working.
Will my truck run without the lift pump? Yes it will. How well? Well, to some it will be very noticeable when it’s not working. Some may not even notice.
If I don’t notice that my lift pump isn’t working, I’m okay right? Not exactly. That means that your expensive injection pump is doing all the work in the fuel system. This is NOT a desirable thing. Plus you are setting yourself up for problems*.
How can I tell if my lift pump is working? Do the famous “lift pump test.” How do you accomplish this highly scientific experiment you ask? Very simple. Pop the hood - you’re half way there. Find on the front top of the engine the thermostat housing. You should see a little T-handle valve standing proud there in front of you. (If you have a van, you’ll have a schrader valve down deep behind the oil fill) That T-valve is calling your name saying “turn me.” Pay attention, ‘cause there’s a hose on the end of the T-valve. That hose should have diesel fuel come out of it when the engine is idling and you open the T-valve. When you open the T-valve and the engine is idling, and no fuel comes out, you’ll hear your engine cough, sputter, and die within 30 seconds. If it doesn’t cough, sputter and die with the T-valve open and no fuel coming out, something is plugged up in your fuel system between the fuel filter cannister and the t-valve, perhaps even inside the fuel filter cannister.
If the engine does die, it has emptied the fuel cannister and run out of fuel, so you will need to close the T-valve, then troubleshoot and repair the lift pump system, as follows in the text below.
Now, if you get a continuous stream of fuel out the hose, then close the T-valve and open the plastic air-bleed valve on the top of the metal filter cap - if fuel spurts out there, then congratulations! You are the proud owner of a working lift pump. Not everyone is as blessed as you are at this moment. If you're not, keep reading.
To those not as blessed, pickup reading here. You must determine why you have no fuel supply coming to your injection pump. There are two main culprits to the demise of a lift pump. Either it’s out to lunch, or it’s in the morgue. See, one means it still might work, the other means it’s dead. How do you tell? Check to see if it has power.
First, find the lift pump under the truck. With the engine idling along, pull the plug for the lift pump. You can either use a test light, or a meter to see if you have voltage at the pins. Make sure you get a good connection, otherwise you may condemn the wrong thing. Sometimes it is difficult to get a probe to meet up with the pins inside the plug, so make double sure you’ve got it.
If you have voltage, *chances* are you have a dead lift pump. Not always, but could be a dead lift pump. You may have voltage present under a "no load" condition. This means that voltage may be present when the lift pump is not attached to the circuit, but once the lift pump is connected, the load exceeds the amount of power the circuit can provide because the OPS contacts are creating a high resistance.
Now, if you don’t have voltage, you’ll have to verify upstream from there why there is no voltage present. What is upstream? The infamous OPS (Oil Pressure Switch), or fuse.
What does the OPS have to do with the lift pump? Doesn’t sound right does it to have oil pressure tied to fuel does it? Well, some think that it is a fail safe that in case your engine ever lost oil pressure, it would shut off the lift pump so that engine would stall. Guess what? If you read a little bit ahead of this paragraph, you’ll find 'dat ain’t so'. The real reason why this circuit even exists is because of an accident. In case you should be in a wreck, the last thing you would need is to have your lift pump going to town pumping out that precious, expensive, fuel all over the accident scene. After all, should you be bleeding and having a thumpin’ head - the last thing you’ll be thinking is “Hey, I just paid $2.50 a gallon for that, somebody get a shop-vac!”
Why would the OPS not allow my lift pump to work? Well, from time to time, or shall we say in the corporate world, from dime to dime, some decisions get made. Some for the good, and some for the good of the keepers of the money. The OPS has a set of contacts inside to power the lift pump. This set of contacts are not heavy enough to carry the pathetic amount of current to the lift pump. Sad, I know, but true. So, what ends up happening is your lift pump works fine, but the OPS gets smoked, and then it quits. You think the pump is bad, but it’s not.
Can I just eliminate the OPS? Well, be careful, it is a safety device in some people’s eyes, and to the rest of us, a pain in the rump. Eyes, rump, pick your part. Anyway. If you just “jump past” the OPS, then your pump will run all the time. Not just all the time, but ALL THE TIME. Christmas and Easter included. It will stop when your batteries are dead. Because, while you are grocery shopping, that pump is running. While you are down for a long winter’s nap, it’s pumping. Doesn’t matter if the key is on or off, it’s pumping.
You can make up another circuit and repower it some other way, but be careful how you do it. Some methods have kept the truck running after the ignition is shut off and keys in pocket.
Back to our little friend the lift pump.
The lift pump may fail in a variety of different ways. It may fail “open” meaning that the coil driving the pump no longer has continuity. It may fail mechanically where it is just frozen and nothing moves. It may even (not as often) fail to pump. This means, it makes noise, but doesn’t actually pump.
Does the lift pump make noise? Yes it does. The model year of your truck will determine if your lift pump is powered during the Wait To Start period. That’s the time where that light is on before actually starting your engine. '96-up OBD2 models pre-run the lift pump during WTS and during START, '94-'95 OBD1 models pre-run the lift pump only during START.
The lift pump is characterized by a kind of “purring” noise heard beneath the truck. That noise is quickly drowned out by the engine, once started. When you shut your engine off, you will hear that pump run briefly, maybe only a quick second or two. If you shut your engine off when cold, you will hear the pump run much longer, sometimes up to 30 seconds or more.
A loud clacking noise would indicate no fuel from the tank, or the lift pump is failing or failed - it will run without pumping fuel when the one-way valve(s) fail.
A faint purring or vibration when touching the lp body indicates it is running, but the internal valve-shuttle armature is stuck due to mechanical failure.
So what kind of problems will it cause if the lift pump isn’t working? Many. It will cause all sorts of fuel related issues*. It can be some of the following:
°Stumbling
°Hard Starting
°Lack of Power
°DTC (Diagnostic Trouble Codes) on the Computer
°Stalling
There are be other* issues too, but these seem to be a very (un)popular list.
Where do I get one of these? Some of our site vendors, or any of the popular auto parts stores, or the dealership. More often than not, the auto parts store is a good bet for Ineeditrightnow.
Diesel Place tip: Ask for the version for the '93 6.5TD truck - it is a direct-fit HD replacement that will supply increased fuel pressure and volume to the Inj Pump, which is a good improvement for the '94-up EFI trucks.
FYI: don't mention that you have a '94-up truck, or you will just confuse the parts guy\gal - just describe your truck and drivetrain as a '93.
The ACDelco or Delphi lift pumps are the best replacement, which you can get from O'Reilley's or NAPA , and some of the site vendors, such as Heath Diesel.
Also FYI: the parts-guy\gal may call it a fuel pump.
Are they difficult to change? No - loosen the tubing-fitting nuts on either end, remove and reinstall. Now, if it were only really that easy. Let’s get real here, no camera out-takes…. You’ll end up getting a Diesel bath. You see, depending upon how much fuel is in your tank, there will be fuel that wants to come out of the fuel line. Be ready, because your chances of a date after changing that lift pump dwindle a bunch, unless they are really into the smell of a Diesel cologne. J
After the successful fuel lift system repair you will need to refill the fuel filter cannister - after opening the air-bleed valve, which is the plastic nut on the very top of the metal cap, power up the lift pump, then close the air bleed when the bubbles stop and fuel begins spurting out - if you still get no fuel, you likely have a stopped-up fuel filter - no need to tell you what to do in that event, right?
FYI: after successful fuel flow out the air-bleed, the engine may take a while to restart and run as the Inj Pump begins to draw fuel from the filter, fills internally, then starts pump-up to 1900psi injection pressures.
#3
10-19-2010, 11:32 AM
Thank you very much for that, I printed it off so I can take it home after work tonight and try it. I do know I can here it when I turn the key on when I'm waiting to start so hopefully it is working. The PDM, I believe it is, is still mounted on top of the motor and I found the kit to move it, is the front bumper the best place to move that to? Thanks for all your help
#4
10-19-2010, 11:37 AM
Here some more reading for this could be way you also seeing blow by at fuller tube
The CDR cannister, affectionately known as the "tuna can", is a Positive Crankcase Ventilation system for Diesels.
It provides regulated low-vacuum, about 1" at idle to 4 to 6 inches WC at full load, from the engine air intake path to remove blow-by gases from the crankcase, and prevent oil leaks.
The PCV valve is designed for engines with a throttle plate across the air inlet path, which causes high vacuum in the intake manifold. High at idle, vacuum will decrease under load, as the throttle is opened, but will greatly increase during vehicle deceleration, when the throttle plate is closed.
The PCV device is a small two-level valve, for both normal and deceleration vacuum levels, and is part of a fresh-air ventilation system. It usually contains a spring tailored to engine size to ensure shuttle valve closure, which works in conjunction with shuttle weight against gravity.
The system must be ported to fresh air because valve guide and piston ring blow-by are not (hopefully) higher than vacuum demand, typically 20" at idle, which would draw air, dirt, water,oil, etc, thru the various engine seals without the filtered fresh air source in the air filter housing.
The Diesel engine, on the other hand, generates vacuum under opposite conditions - almost none at idle, more as engine speed increases. Diesels have no throttle plate to restrict intake air flow.
Diesel vacuum is caused by the slight restrictions presented by the air filter and intake path ducting.
A turbocharger increases available vacuum even more, as the compressor draws more air to the inlet under engine load, to produce Boost.
Dirty air filter restriction will increase inlet vacuum in turbo and intake vacuum in non-turbo engines.
The CDR is specifically calibrated for turbo or non-turbo engines, with normal filter deterioration from dirt and dust factored in.
With no great levels of vacuum to draw-thru the crankcase, no fresh air source is needed - it is a closed-crankcase system.
Normal blow-by is low, so vacuum must be regulated such that air is not drawn into the engine thru various seals - crankshaft, valve-stem, oil filler and dipstick tubes. The crankshaft seals assume greatest importance because of location down low in road draft area.
The CDR, Crankcase Depression Regulator, is designed to function with low-level vacuum. The tuna-can size is to accomodate the large silicone rubber\synthetic diaphragm. Vacuum on the diaphragm actuates the valve against a low-pressure spring, calibrated for turbo or non-turbo applications, which also functions to ensure that the valve opens as vacuum decreases.
Fully open at idle, it will begin to close as power demand and vacuum increases, regulating the 'depression' in the crankcase such that excessive oil is not drawn out of the engine, and blow-by pressure in the crankcase does not increase.
It is not a one-way valve, but closure is toward the vacuum source. It opens under crancase 'back-fire' conditions, and would become a 'no-way' valve if the diaphragm ruptured, allowing excessive vacuum to develop in the crankcase.
Because blow-by vapor is drawn into the turbo inlet, oil will accumulate in the inlet area, but is not cause for concern unless the quantity approaches a quart a month. Excess vapor from worn piston rings can cause engine surging, as vapor is drawn into cylinder and ignited along with injected fuel, which is a light oil.
Non-Diesel oils vaporize more easily due to higher pressures and temperatures encountered in Diesel service, particularly those in the turbocharger housing.
<><><><><><><><><>CDR TESTING<><><><><><><><><>
CDR testing can be accomplished with 4' section of clear plastic tubing, sized to fit the dipstick tube, ~3/8".
Form a 3" U-bend , with 12" vertical columns. This could be attached to a piece of 1 x 6 with large u-staples, parallel-spaced at one inch intervals for indication of measurement.
Important - do not crush or deform the plastic tubing.
Place the free end over the dipstick tube, ensuring tight fit, with no leak-by. Position the manometer vertically, where the upper end of the U is lower than the end over the dipstick tube.
Note: this is to prevent water siphoning into the oil pan thru the dipstick tube.
Pour colored water into the U section such that about 6 " of water is in each leg, about 4 - 6" below the top of the open end.
Have someone start the engine, bring the rpm up to about 2000, keeping close watch on the water level in the U-tube. If the water in the dipstick leg rises an inch, the water in the open leg will drop an equal amount. Adding the drop level to the rise level, this would indicate vacuum at two inches on the Water Column.
Vacuum at idle should be around 1", depending on air filter restriction; at 2000 rpm, the CDR should limit vacuum to 4 - 6" WC on a calibrated Manometer. The shade-tree version should indicate close to those figures, depending on accuracy of staple intervals.
If the level in the dipstick leg drops, and the open leg level rises, this indicates the crankcase is slightly pressurized.
27" WC is equal to 1 PSI (Pound per Square Inch) 1psi is equal to 2" mercury
Atmospheric pressure is 14.7 psi, or 29" mercury, or 396" WC, rounding off
<><><><><><><><><><><><><><><><><><><><><><><>
The CDR should never be solvent-cleaned, as various solvents can dissolve the diaphragm, again resulting in a 'no-way' valve.
Some truck manuals indicate replacment at 30,000 miles. This refers to the early style CDR and oil-cap breather system, used up through mid-'80s. By '88 - '89, the CDR system had been revised to its present configuration, where the CDR cannister is on the passenger-side valve cover, with one external connecting hose to the intake system.
Early failure-prone systems can be easily upgraded to the late setup - 1 valve cover with grommet seal, 1 CDR, 1 hose.
Replace the CDR in the late systems when it fails the Manometer water column test.
__________________
The CDR cannister, affectionately known as the "tuna can", is a Positive Crankcase Ventilation system for Diesels.
It provides regulated low-vacuum, about 1" at idle to 4 to 6 inches WC at full load, from the engine air intake path to remove blow-by gases from the crankcase, and prevent oil leaks.
The PCV valve is designed for engines with a throttle plate across the air inlet path, which causes high vacuum in the intake manifold. High at idle, vacuum will decrease under load, as the throttle is opened, but will greatly increase during vehicle deceleration, when the throttle plate is closed.
The PCV device is a small two-level valve, for both normal and deceleration vacuum levels, and is part of a fresh-air ventilation system. It usually contains a spring tailored to engine size to ensure shuttle valve closure, which works in conjunction with shuttle weight against gravity.
The system must be ported to fresh air because valve guide and piston ring blow-by are not (hopefully) higher than vacuum demand, typically 20" at idle, which would draw air, dirt, water,oil, etc, thru the various engine seals without the filtered fresh air source in the air filter housing.
The Diesel engine, on the other hand, generates vacuum under opposite conditions - almost none at idle, more as engine speed increases. Diesels have no throttle plate to restrict intake air flow.
Diesel vacuum is caused by the slight restrictions presented by the air filter and intake path ducting.
A turbocharger increases available vacuum even more, as the compressor draws more air to the inlet under engine load, to produce Boost.
Dirty air filter restriction will increase inlet vacuum in turbo and intake vacuum in non-turbo engines.
The CDR is specifically calibrated for turbo or non-turbo engines, with normal filter deterioration from dirt and dust factored in.
With no great levels of vacuum to draw-thru the crankcase, no fresh air source is needed - it is a closed-crankcase system.
Normal blow-by is low, so vacuum must be regulated such that air is not drawn into the engine thru various seals - crankshaft, valve-stem, oil filler and dipstick tubes. The crankshaft seals assume greatest importance because of location down low in road draft area.
The CDR, Crankcase Depression Regulator, is designed to function with low-level vacuum. The tuna-can size is to accomodate the large silicone rubber\synthetic diaphragm. Vacuum on the diaphragm actuates the valve against a low-pressure spring, calibrated for turbo or non-turbo applications, which also functions to ensure that the valve opens as vacuum decreases.
Fully open at idle, it will begin to close as power demand and vacuum increases, regulating the 'depression' in the crankcase such that excessive oil is not drawn out of the engine, and blow-by pressure in the crankcase does not increase.
It is not a one-way valve, but closure is toward the vacuum source. It opens under crancase 'back-fire' conditions, and would become a 'no-way' valve if the diaphragm ruptured, allowing excessive vacuum to develop in the crankcase.
Because blow-by vapor is drawn into the turbo inlet, oil will accumulate in the inlet area, but is not cause for concern unless the quantity approaches a quart a month. Excess vapor from worn piston rings can cause engine surging, as vapor is drawn into cylinder and ignited along with injected fuel, which is a light oil.
Non-Diesel oils vaporize more easily due to higher pressures and temperatures encountered in Diesel service, particularly those in the turbocharger housing.
<><><><><><><><><>CDR TESTING<><><><><><><><><>
CDR testing can be accomplished with 4' section of clear plastic tubing, sized to fit the dipstick tube, ~3/8".
Form a 3" U-bend , with 12" vertical columns. This could be attached to a piece of 1 x 6 with large u-staples, parallel-spaced at one inch intervals for indication of measurement.
Important - do not crush or deform the plastic tubing.
Place the free end over the dipstick tube, ensuring tight fit, with no leak-by. Position the manometer vertically, where the upper end of the U is lower than the end over the dipstick tube.
Note: this is to prevent water siphoning into the oil pan thru the dipstick tube.
Pour colored water into the U section such that about 6 " of water is in each leg, about 4 - 6" below the top of the open end.
Have someone start the engine, bring the rpm up to about 2000, keeping close watch on the water level in the U-tube. If the water in the dipstick leg rises an inch, the water in the open leg will drop an equal amount. Adding the drop level to the rise level, this would indicate vacuum at two inches on the Water Column.
Vacuum at idle should be around 1", depending on air filter restriction; at 2000 rpm, the CDR should limit vacuum to 4 - 6" WC on a calibrated Manometer. The shade-tree version should indicate close to those figures, depending on accuracy of staple intervals.
If the level in the dipstick leg drops, and the open leg level rises, this indicates the crankcase is slightly pressurized.
27" WC is equal to 1 PSI (Pound per Square Inch) 1psi is equal to 2" mercury
Atmospheric pressure is 14.7 psi, or 29" mercury, or 396" WC, rounding off
<><><><><><><><><><><><><><><><><><><><><><><>
The CDR should never be solvent-cleaned, as various solvents can dissolve the diaphragm, again resulting in a 'no-way' valve.
Some truck manuals indicate replacment at 30,000 miles. This refers to the early style CDR and oil-cap breather system, used up through mid-'80s. By '88 - '89, the CDR system had been revised to its present configuration, where the CDR cannister is on the passenger-side valve cover, with one external connecting hose to the intake system.
Early failure-prone systems can be easily upgraded to the late setup - 1 valve cover with grommet seal, 1 CDR, 1 hose.
Replace the CDR in the late systems when it fails the Manometer water column test.
__________________
#5
10-19-2010, 12:28 PM
#7
10-20-2010, 07:55 AM
, I checked the rod on the turbo and it takes a lot to move it with the engine running so I guess thats good from what I read. Now I just have to check my tuna can. I appriciate all the help.
